The present invention relates to medical examination tables; and more particularly, it relates to a mechanism for horizontally adjusting and locking in place left and right stirrup assemblies extending from the foot of the table.
Heretofore, the horizontally extensible rods which support the stirrup assemblies for a medical examination table have been locked in their horizontal adjustment by means of a hand wheel with a threaded stud that is received in the side of the table and adapted to engage and secure the rod after it has been adjusted to the proper distance from the table. This has normally required the use of both hands, one for unloosening the turn wheel and the other for adjusting the extension of the rod. A further disadvantage in the use of prior adjustment assemblies for stirrup extension rods is that during use, the normal up and down forces applied to the stirrup assembly tend to wiggle the rod and to loosen the tightening screw on the hand wheel.
In the present invention, a rectangular channel with a flat top wall is provided in the examination table for receiving a corresponding rectangular extension bar provided at its distan end with a stirrup assembly. A separate mechanism is included for permitting vertical and angular adjustment of the stirrup assembly, but it forms no part of the present invention.
A first brake pad is affixed to the upper inner surface of the extension bar so that it is carried along with it during adjustment. A second brake pad is secured to the lower surface of the channel adjacent its mouth. There is a slight vertical clearance provided in the channel so that the rod may be moved back and forth in the unlocked position which is achieved by lifting the stirrup assembly upwardly. When the stirrup assembly is placed in its proper horizontal adjustment and released, the normal gravity force on the stirrup assembly pivots the innermost end of the rod about the second brake pad adjacent the mouth of the channel until the first brake pad on the top of the rod engages the top of the channel, thereby applying braking action at two positions to lock the rod in place and prevent against further horizontal adjustment.
The channel walls are enameled still and the pads may be rubber or neoprene. In either case there is a coefficient friction of about 0.9 between the pads and walls which, as will be discussed further within, results in combined frictional holding forces at least twice as great as the maximum encountered force on the stirrup tending to further extend it. Hence, the bar is locked in place.
During normal use, the additional downward force exerted by the leg being supported or by any downward pressure applied by the person being treated or examined, (which is the normal occurrence) will cause a further pressure on the brake pads, thereby resulting in an even greater frictional engagement between the extension bar and the channel to prevent horizontal movement of the bar from the adjusted position.
Thus, the present invention provides an adjusting and locking mechanism in which the horizontal extension bar is released from its locked position simply by raising the stirrup assembly, and adjustment is achieved by sliding the bar to its desired length. In addition, the normal forces encountered during use tend to achieve an even greater locking force on the adjustment assembly.
Other features and advantages of the present invention will be apparent to persons skilled in the art from the following detailed description of a preferred embodiment accompanied by the attached drawing wherein identical reference numerals will refer to like parts in their various views.